Method of preparation of extracts of hops

ABSTRACT

A method of preparation of extracts of hops by means of one or more organic solvent, this method comprising the isomerization of the hop acids and includes isomerizing the Alpha -acids of the hops in the presence of a solvent selected from among the group comprising isooctane and methyl cyclohexane.

United States Patent Verzele 115] 3,686,316 [451 Aug. 22,1972

[54] METHOD OF PREPARATION OF EXTRACTS OF HOPS Inventor: Maurice G. E.Verzele, l3, Krijgslaan, Gent, Belgium Filed: Jan. 8, 1968 Appl. N0.:696,139

us. Cl. ..260/586 R, 99/505 Int. Cl. C070 45/00, C 1 2c 9/02 Field ofSearch IN/50.5; 260/666. 586

[56] References Cited UNITED STATES PATENTS 3,212,854 10/1965 Betts eta1. ..99/50.5 X 3,298,835 l/ 1967 Hildebrand et al ..99/50.5 3,364,2651/1968 Klingel et al ..260/586 3,433,642 3/ 1969 Nakayama et a1...99/50.5

FOREIGN PATENTS OR APPLICATIONS 5/1961 Canada ..99/50.5

OTHER PUBLICATIONS Goedkoop et al., Beer Substances Extractable byChloroform and [so-octane," Journal of the Institute of Brewing, Vol.70, 1964, p. 365.

Standen, A. (ed), Encyclopedia of Chemical Technology, lntersciencePublishers, New York, 1965, p. 675.

Primary Examiner-Joseph M. Golian A!!0rney-Sughrue, Rothwell, Mion, Zinn& Macpeak 5 7] ABSTRACT 12 Claims, No Drawings METHOD OF PREPARATTON OFECTS F HOPS The present invention relates to a method of preparation ofextracts of hops by means of one or more organic solvent, this methodcomprising the isomerization of the hop acids in order to transform thea-acids into iso-a acids.

The operation of putting hops in the beer includes processing the wortby the hops at boiling temperature so as to transfonn the a-acids intoiso-a acids, the latter being more soluble and more bitter than theformer.

Yield of this reaction in the wort does not exceed 5 5 percent and,moreover, part of the iso-a acids is eliminated in the course offermentation and of the operations following the latter, so that theactual yield in the beer is only 25 to 35 percent.

4 It is known, in order to improve the yield of isomerization, toprepare extracts of hops by means of powerful organic solvents, such asthe ketones, the alcohols, the chlorinated hydrocarbons. These extractsare then boiled with the wort, just like the hops.

The yield of isomerization achieved with the help of these methodsslightly exceeds that achieved by conventional methods of putting hopsin the beer, but the losses are just as substantial.

It is also known to prepare extracts of hops containing already iso-aacids, the latter being obtained by placing the said extracts in thepresence of aqueous alkali and by heating the solution prepared in thismanner so as to transform the a-acids into iso-a acids.

The known methods to obtain such isomerized extracts are very intricateand call for important and costly installations. I

The object of the present invention consists essentially in overcomingthis disadvantage by the very judicious selection of an a-acid selectiveextraction solvent.

For that purpose the method according to the invention includesisomerizing the a-acids of the hops in the presence of a solventselected from among the group comprising isooctane and methylcyclohexane.

According to a form of embodiment of the invention, the method includesadding to a solution comprising the said organic solvent and a-acids ofhops and alkaline solution, heating the mixture thus obtained in orderto transform the a-acids into iso-a acids, acidifying this mixture,separating an organic phase from an aqueous phase of the mixture andsubmitting the organic phase to evaporation until a syrupy pastecontaining the iso-a acids is obtained.

According to an advantageous form of embodiment of the invention themethod includes adding to a solution comprising the said organic solventand a-acids of hops an alkaline solution, heating the mixture thusobtained in order to transform the a-acids into iso-a acids, separatingthe aqueous phase from the organic phase of the mixture and extractingthe iso-a acids from the aqueous phase.

According to a particularly advantageous form of embodiment of theinvention, the method according to the invention includes bringing theaqueous solution containing the iso-a acids to a pH of 7 magnitude,processing subsequently this solution with a saturated hydrocarbon,separating the aqueous and organic phases achieved, bringing the aqueousphase to a pH of 3 magnitude, extracting the iso-oz acid from thisaqueous phase by means of a solvent not miscible with water anddissolving the iso-a acid, separating the solvent containing the iso-aacid and lastly collecting the iso-a acid by evaporation of the solvent.

Other details and features of the invention will become apparent fromthe description given hereinafter, by way of non limitative example, ofa method of preparation and purification of extracts of hops accordingto several forms of embodiment.

in a first form of embodiment of the invention, the method ofpreparation of extracts of hops includes, in a first stage, carrying outan extraction with hops or not isomerized extracts of hops by means ofan a-acids selective solvent. This solvent is advantageously selectedfrom among saturated hydrocarbons having a boiling point close to C.According to the invention, solvents such as the isooctane or the methylcyclohexane are particularly suitable. These solvents make it possibleto achieve a very thorough separation between the a-acids and the othersubstances of the hops or of the extract of hops worked, so that thesubsequent isomerization reaction of the a-acids into iso-a acids maytake place under very favorable conditions. indeed, the presence of ahigh proportion of substances other than the a-acids in the reactivemedium inhibits the isomerization reaction.

in a second stage of themethod according to the invention to thesolution comprised of the said solvent and the hops or extract of hopsis added an alkaline solution which is for preference an aqueoussolution of sodium carbonate, and the mixture thus obtained is heated toa temperature close to the boiling temperature, so as to transform thea-acids into iso-a acids.

This mixture, comprising an organic phase and an aqueous phase, isacidified in a third stage, so that the said iso-a acids pass into theorganic phase.

Subsequently, in a fourth stage, the aqueous phase is separated from theorganic phase and the latter is subjected to evaporation in vacuo inorder to eliminate the solvent, until a syrupy paste containing theiso-a acids is obtained.

The said aqueous phase may eventually be subjected to a new extractionby the addition of a new volume of solvent followed by a separation ofthe new aqueous and organic phases and by an evaporation of the solventfrom the organic phase. This additional extraction operation may berepeated with the obtained aqueous phases until the quantity of iso-aacids contained in the aqueous phase becomes negligible.

In a second form of embodiment according to the invention the method ofextraction includes, in a first stage, carrying out, same as in themethod according to the first form of embodiment, an extraction fromhops or from non isomerized extracts of hops by means of isooctane ormethyl cyclohexane and, in a second stage, isomerizing the a-acids iniso-a acids by the addition of an aqueous solution of sodium carbonate,so as to obtain a pH 10 and subsequently heating the mixture thusobtained.

The method according to this second form of embodiment differs from themethod according to the first form of embodiment by the fact, that inthe method according to the second form of embodiment, the organic andaqueous phases obtained in the said second stage are separated withoutfirst carrying out an acidification of these two phases.

The said pH aqueous phase containing the iSO-a acids is brought to pH 7.Subsequently a quantity of vent not miscible with water and dissolvingthe iso-a acid, this solvent being for preference a chlorinatedhydrocarbon, such as methylene chloride. Following evaporation of thesolvent, a syrupy mass of high purity and rich in free iso-a acids isobtained.

The free iso-a acids contained in the isomerized extract obtained inthis manner are able to impart the bitter taste to the beer, but arestill little soluble in water. In order to overcome this disadvantage,the final stage of the method according to the invention includestransforming these free iso-a acids into a salt more soluble in waterthan these iso-a acids. Advantageously, the isomerized extract of hopscontaining the free iso-a acids is processed with an aqueous solution ofpotassium or sodium carbonate in order to produce the potassium orsodium salt of the iso-a acids, salts which are perfectly soluble inwater and in beer.

The said saturated hydrocarbon used in the said intermediate stage beingfor preference comprised vof isooctane or of methyl cyclohexane, theorganic phase achieved by extraction by means of this hydrocarbon isadded to the organic phase following isomerization.

- The solvent contained in this organic phase may be trated by thefollowing examples EXAMPLE I To a volume of methyl cyclohexane solutioncontaining 50 g of a-acids per liter are added four volumes of watercontaining 0.3 gram-equivalents of sodium carbonate per liter. Themixture is brought to a boil under good stirring and the reflux is heldfor 90 minutes. After cooling the aqueous phase is acidified withsulfuric acid.

The mixture separates into two layers; the organic layer is removedafter which a volume of methyl cyclohexane is added to the aqueousphase. Thus a second extraction of the aqueous phase is carried out.

The two organic fractions are evaporated in vacuo and the isomerizedextract of hops is obtained which has the form of a greenish syrupypaste.

The method according to the invention may be illus-- EXAMPLE llcyclohexane on the crushed flowers of hops is kept in solution in thissolvent so as toobtain a concentration of 50 grams of a-acids per liter.To one volume of this solution are added four volumes of watercontaining 0.3 gram-equivalents of sodium carbonate per liter. Themixture is brought to a temperature of 87 C under good stirring andthese conditions are maintained for 90 minutes. The aqueous phaseseparated from the organic phase is brought to ph 7 by means of dilutedsulfuric acid andthen extracted with one-half volume of methylcyclohexane. The aqueous phase, separated from this organic phase, isthen acidified up to pH 3 by means of sulfuric acid and then extractedthree times with one-half volume of methylene chloride. The solvent iscompletely evaporated, which yields a yellowish syrupy paste'containingthe iso-a acids.

The extract thus obtained is then processed with an aqueous solution ofpotassium carbonate so asto form the potassium salt of the iso-a acidswhich has the form of a light brown syrupy mass, which is well able todissolve in water and in beer.

It is well understood the the invention is not limited to the forms ofembodiment described and that many modifications may be contemplatedwithout departing from the scope of the present patent application.

I claim:

1. A method of preparing iso-a-acids from extracts of hops comprising 1.preparing an extract of hops containing a-acids of the hops in anorganic solvent selected from the group consisting of iso-octane andmethylcyclohexane,

2. mixing said solvent extract with an aqueous alkaline solution forminga mixture comprising an aqueous phase and an organic phase,

3. isomerizing the a-acids of the hops into iso-a-acids in said mixtureand thereby in the presence of said solvent, and

4. recovering the iso-a-acids. mixture of 2. The method as claimed inclaim 1, wherein the isomerizing is by heating, and wherein therecovering of the iso-a-acids comprises the steps of acidifying themixture of the aqueous phase and. the organic phase, separating theorganic phase from the aqueous phase, and evaporating the organic phaseto a syrupy paste.

3. The method as claimed in claim 2, wherein the recovering of theiso-a-acids subsequent to the separating of the organic phase from theaqueous phase includes additionally repeatedly extracting any remainingiso-a-acids from the aqueous phase by adding an additional quantity ofan organic solvent to the aqueous phase, separating the aqueous andorganic phases, and combining said organic phases.

4. The method as claimed in clairn 2, wherein said extract containsabout 50 g of a-acids per liter of said organic solvent.

5. The method as claimed in claim 4, wherein said aqueous alkalinesolution is addedat a volume ratio to the extract of 4:1 and whereinsaid aqueous alkaline solution comprises 0.3 gram-equivalents of sodiumcarbonate per liter of solution.

6. The method as claimed in claim 2, wherein the heating of the mixtureis by refluxing the mixture with good stirring for minutes or longer.

7. The method as claimed in claim 1, wherein the isomerizing is byheating and wherein the recovering comprises separating the aqueousphase from the organic phase, and extracting the iso-a-acids from theaqueous phase.

8. The method as claimed in claim I, wherein the isomerizing is byheating and wherein the recovering comprises separating the aqueousphase from the organic phase, bringing the aqueous phase containing theiso-a-acids to a pH of 7, adding a saturated hydrocarbon to the aqueousphase forming an aqueous phase and an organic phase, separating theaqueous and organic phases, bringing the aqueous phase to a pH of 3,extracting the iso-a-acids from the aqueous phase with an'organicsolvent not miscible with water to dissolve the iso-a-acids, separatingthe organic solvent containing the iso-a-acids and collecting theiso-a-acids by evaporation of the solvent.

9. The method as claimed in claim 1, wherein said method subsequent torecovering the iso-a-acids additionally comprises converting theiso-a-acids into the salts thereof, in which said salts formed are moresoluble in water than the free iso-a-acids.

10. The method as claimed in claim 9, wherein said

2. The method as claimed in claim 1, wherein the isomerizing is byheating, and wherein the recovering of the iso- Alpha -acids comprisesthe steps of acidifying the mixture of the aqueous phase and the organicphase, separating the organic phase from the aqueous phase, andevaporating the organic phase to a syrupy paste.
 2. mixing said solventextract with an aqueous alkaline solution forming a mixture comprisingan aqueous phase and an organic phase,
 3. isomerizing the Alpha -acidsof the hops into iso- Alpha -acids in said mixture and thereby in thepresence of said solvent, and
 3. The method as claimed in claim 2,wherein the recovering of the iso- Alpha -acids subsequent to theseparating of the organic phase from the aqueous phase includesadditionally repeatedly extracting any remaining iso- Alpha -acids fromthe aqueous phase by adding an additional quantity of an organic solventto the aqueous phase, separating the aqueous and organic phases, andcombining said organic phases.
 4. The method as claimed in claim 2,wherein said extract contains about 50 g of Alpha -acids per liter ofsaid organic solvent.
 4. recovering the iso- Alpha -acids.
 5. The methodas claimed in claim 4, wherein said aqueous alkaline solution is addedat a volume ratio to the extract of 4: 1 and wherein said aqueousalkaline solution comprises 0.3 gram-equivalents of sodium carbonate perliter of solution.
 6. The method as claimed in claim 2, wherein theheating of the mixture is by refluxing the mixture with good stirringfor 60 minutes or longer.
 7. The method as claimed in claim 1, whereinthe isomerizing is by heating and wherein the recovering comprisesseparating the aqueous phase from the organic phase, and extracting theiso-Alpha -acids from the aqueous phase.
 8. The method as claimed inclaim 1, wherein the isomerizing is by heating and wherein therecovering comprises separating the aqueous phase from the organicphase, bringing the aqueous phase containing the iso- Alpha -acids to apH of 7, adding a saturated hydrocarbon to the aqueous phase forming anaqueous phase and an organic phase, separating the aqueous and organicphases, bringing the aqueous phase to a pH of 3, extracting theiso-Alpha -acids from the aqueous phase with an organic solvent notmiscible with water to dissolve the iso- Alpha -acids, separating theorganic solvent containing the iso- Alpha -acids and collecting the iso-Alpha -acids by evaporation of the solvent.
 9. The method as claimed inclaim 1, wherein said method subsequent to recovering the iso- Alpha-acids additionally comprises converting the iso- Alpha -acids into thesalts thereof, in which said salts formed are more soluble in water thanthe free iso- Alpha -acids.
 10. The method as claimed in claim 9,wherein said salts are selected from the group consisting of the sodiumsalts and the potassium salts.
 11. The method as claimed in claim 8,wherein the saturated hydrocarbon in the recovering is selected from thegroup consisting of iso-octance and methyl cyclohexane.
 12. The methodas claimed in claim 8, wherein the organic solvent not miscible withwater is a chlorinated hydrocarbon.